Researchers are trying to find out why more female pygmy hippos are born in captivity than males.
Scientists hope to discover why 60% of the species' offspring born in captivity are female and whether this happens in the wild.
It is hoped the study, funded by the Royal Zoological Society of Scotland (RZSS), which owns Edinburgh Zoo, will help stop the species becoming extinct.
Hippos are being monitored in the Tai National Park, Cote d'Ivoire, Africa.
The project is being co-ordinated by the Institute of Breeding Rare and Endangered African Mammals (Ibream).
In the 1990s an estimated 3,000 pygmy hippos lived wild but experts believe that figure may have been exaggerated.
The RZSS's Iain Valentine said: "For scientists to ensure genetic diversity in captive stocks, it is important to work out why genetically valuable females may not be breeding.
"But to do this we need better understanding of the natural cycles to make sure that we can do all we can in the captive environment.
"That is why RZSS is part of this pioneering conservation partnership and is funding primary research that will help the whole zoo community.
"This will hopefully give this species of hippo a fighting chance in the wild."
Ibream is studying faeces samples from 15 European zoos, including Edinburgh, to learn more about female hippos' monthly cycles and if hormones found in them can show whether they are pregnant or not.
Edinburgh Zoo is home to three pygmy hippos, with one female born last year.
Ibream's Dr Monique Paris said: "There are clear reasons as to why populations have declined in the wild, such as habitat loss and hunting, but for those working with captive populations there are equally puzzling questions.
"With the endangered status of the hippo, maintaining a viable population in captivity is important.
"However, for every two males born, three female babies are born, making zoo management complex.
"We are also dealing with extremely shy animals with little knowledge of their natural behaviour and therefore we really don't know if this is purely a natural reproductive phenomenon or one restricted to the captive environment."